1. Field of the Invention
This invention relates to ionic polymers. More particularly, this invention relates to quaternary phosphonium salts of anionic polymers, i.e. polymers containing covalently bound negatively charged groups. Most particularly, this invention is concerned with novel compositions of matter comprising quaternary phosphonium salts of polymers having incorporated therein one or more covalently bonded anionic radicals selected from the group consisting of sulfonic, carboxylic and phosphonic acid radicals.
The ionic salts of this invention may be schematically represented, for the case where the anionic group is a sulfonic acid radical, as follows: ##STR1## wherein C is one of a plurality of carbon atoms comprising a portion of the polymer. Backbone chain of carbon atoms or is in an acyclid, alicyclic, or aromatic radical which is pendant to the backbone chain and wherein said .about.C.about. is (1.) in a single polymer molecule, (2.) in the same polymer molecule, and (3.) in different polymer molecules; R', R", R"' and R'.sup.v are independently selected from the group consisting of C.sub.1 to C.sub.50 straight and branched chain acyclic, alicyclic, aryl, alkylaryl and arylalkyl radicals and substituted functional derivatives thereof; and Q is selected from the group consisting of C.sub.1 to C.sub.40 divalent straight and branched chain alkylene cycloalkylene, arylene, dialkylene-arylene radicals and substituted functional derivatives thereof and --(CHY).sub.n --Z.sub.m --(CHY).sub.n wherein Z is a hetero atom selected from the group consisting of oxygen and sulfur, m is zero or one, Y is hydrogen or said C.sub.1 to C.sub.50 radicals or substituted functional derivatives of said radicals and n is an integer of from 1 to 10.
While the mono and divalent quaternary phosphonium salts of anionic polymers shown in the above formulae are preferred, this invention also includes polyvalent quaternary phosphonium salts of anionic polymers wherein the polyvalent phosphonium cations have the general formulae: EQU [R'R"R'"P.sup.+ ]Q[(R')P.sup.+ (R")]Q[P.sup.+ R'R"R"'] 4
wherein R', R", R"' and Q have the same value and significance as in formulas 2. and 3. above; and EQU T [PR'R"R"'].sub.v.sup.+
wherein v is the valency of a polyvalent hydrocarbon radical T, and R', R" and R"' have the same value and significance as R', R", R"' and R'.sup.v in the above formulas, vs. 3 to 10, preferably 3 or 4.
Using sulfonated polymers as a preferred example of the anionic polymers of this invention, the ionically cross-linked ionomers of this invention are readily prepared from the free-sulfonic acid form by direct neutralization, either in bulk or in solution, with a quaternary phosphonium hydroxide, or by double decomposition (metathesis) of a cationic salt of the sulfonic acid with a quaternary phosphonium salt of an acid which is weaker (i.e. has a lower K.sub.a) than the sulfonic acid, or by double decomposition in a multiphase fluid medium in which the salt of the displaced counterion is selectively removed from the phase containing the polymer to a phase in which the phosphonium ionomer is substantially insoluble.
The properties and utility of the ionic salts of this invention vary over a wide range depending on the structure of the anionic polymer, the average molecular weight and molecular weight distribution, the degree of neutralization of the anionic groups in the polymer, the mole concentration of the quaternary phosphonium salt groups in the polymer, and in particular, the type and variety of the substituents attached to the phosphorus. The ionic salts may vary from water-soluble polyelectrolytes useful as adhesives and thickening agents to elastomers or hard resins which are thermoplastic at elevated temperatures permitting the products to be extruded, injection molded, vacuum formed and sheeted.
A particularly useful form for an ionomer is an elastomer (water-insoluble) which can be melt fabricated and then used without curing, and which can be reprocessed at elevated temperature since they don't contain covalent crosslinks.
2. Prior Art
Anionic polymers and their salts, prepared either by covalently appending anionic groups to a preformed polymer, as for example, by sulfonation or grafting of anionic monomers, or prepared by the mono or interpolymerization of monomers having acid moieties are old in the art but no references in the patent or general chemical literature have been found disclosing quaternary phosphonium salts of anionic polymers. A recently published book, "Ionic Polymers", L. Holliday, Editor, John Wiley & Sons, New York, New York, 1975 reviews the field and describes a variety of anionic polymers suitable for the preparation of the quaternary phosphonium salts of this invention.